Journal of Sustainability Science and Management ISSN: 1823-8556 Volume 6 Number 1, June 2011: 51-59 © Universiti Malaysia Terengganu Publisher MICROSTRUCTURE AND LIFE CYCLE OF METISA PLANA WALKER (LEPIDOPTERA: PSYCHIDAE) CHUA CHIN KOK*1, OOI KOK ENG1, ABDUL RAHMAN RAZAK2, AND ADZEMI MAT ARSHAD2 1DuPont Malaysia Sdn Bhd, Malaysia Field Research Station, Lot 2385, Mukim 3, Lahar Tiang, 13200 Kepala Batas, Seberang Perai Utara, Pulau Pinang, Malaysia. 2Faculty Agro-Technology & Food Science, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia. *Corresponding author: Chin–[email protected] Abstract: The Metisa plana (Lepidoptera: Psychidae), is an important defoliator of oil palm in Southeast Asia. Severe defoliation on palm consequently affects the productivity. The rearing protocol, microstructure, behaviour and life cycle of all stages of M. plana are described. The life cycle of M. plana from egg to adult in this controlled rearing environment was 103.5 days. The larvae of M. plana in this study undergo six larval instars. The larva started feeding immediately upon being laid on the leaf surface. In the larval period, the 1st instar took 9 – 16 days to change into 2nd instar. As the larva developed, it used lichen to build a case that it wore as it fed and grew. The development duration from 2nd instar to 3rd instar was 14 – 17 days. The 3rd instar took the longest period at 16 – 18 days to develop into 4th instar. Development of subsequent instar stages 4th to 5th and 5th to 6th were slightly shorter, between 10 – 15 days and 12 – 16 days respectively. In total, development of 1st through 6th instar stage of M. plana was 71.5 days. KEYWORDS: Metisa plana, oil palm, microstructure, life cycle Introduction important factor for effective treatment (Sidhu and Oil-palm pests have been controlled mainly Saikia, 1999). In different stages of Spodoptera by the use of insecticides, with their attendant frugiperda, instars produced different levels of environmental hazards (Morin and Mariau, feeding and damage to cotton (Luttrell and Mink, 1971). The use of an Integrated Pest-Management 1999). The number of instars increased in adverse (IPM) strategy holds promise for the sustainable conditions when larvae fail to reach a specific management of the oil-palm pests. The components threshold size for metamorphosis (Esperk, et al., of this strategy are phytosanitary surveillance, 2007). cultural, biological control and the selective use Bagworm outbreaks of unprecedented of insecticides. The IPM approach requires a good severity occurred in Malaysian oil-palm reference of the biology of the pest. plantations from the late 1950s to early 1960s. In view of its importance, one of the very initial Until today, the outbreak of bagworm is still steps towards effective bagworm control would continuous even at the same historical area. be to establish and understand the fundamental Complete life cycle of Metisa plana ranges information on biology of the bagworm, such as from 80 to 113 days (Khoo et al., 1991) with a behaviour, structure and life cycle. Knowledge mean of 90 days (Basri and Kevan, 1995). Initial on the biology and full life cycle of M. plana information on M. plana biology was reported by is essential for sound management of this pest. Yunus and Balasubramaniam (1975), but detailed Understanding the life cycle of this insect would information on the behaviour, microstructure and elucidate the appropriate times of spraying, an life cycle of M. plana are still lacking. Therefore, Received: 04 October 2010 / Accepted: 09 February 2011 Chua Chin Kok et al. 52 this study was undertaken to establish the rearing Results and Discussion protocol, microstructure, behaviour and life cycle The Microstructure and Behaviour of Metisa of M. plana for strategic control and management plana of the pest. (a) Larvae of Metisa plana Materials and Methods Early Development of the Larvae Source of Insects and Eggs Sterilisation Process The larvae were lichen, forming a portable case, Cultures of M. plana were established by collecting which they carried around with them as they fed. cocoons from several oil-palm estates having M. The rearing study showed that the average number plana outbreaks in Kepala Batas, Penang. The of neonates (new born larvae) hatched from a outbreak of M. plana was fairly synchronised, single egg mass ranging from 140 – 210 neonates. thus the emergence of the first instar larvae were The difference between mean number of eggs laid reasonably uniform. and emerged neonates could possibly be due to cannibalism by sibling neonates or be unfertile eggs The cocoons were collected from the field (Rhainds and Ho, 2002). Newly-hatched neonate and reared to adults inside a plastic container. was approximately 1 mm and moved actively Eggs laid by the mated females were collected. out through the case of female parent. Some of The black-headed eggs were surface sterilised the weaker neonates died and failed to develop in 1% formaldehyde solution for 15 minutes into 1st instar larvae. Metisa plana larvae were and rinsed under slow-running tap water for polyphagous. Within 1 – 2 hours of emergence, the 10 minutes. A hundred surface-sterilised eggs neonates used plant material to construct a small were picked randomly for hatchability study and case around the posterior region of their body. replicated three times. Non surface-sterilised eggs They were most often seen attached to the adaxial were used as a control. The eggs were placed inside of oil-palm leaf in an upright position. In field a 20ml vial. condition, more often the larvae were hung on long silken threads for dispersal by wind or carriage by Preparation for Scanning Electron Microscopy animals and men. The case was correspondingly (SEM) enlarged and developed, either by widening at the The internal organs of larvae of different instars frontal aperture, or by cutting the side walls and were observed under the scanning electron patching over the incision with a piece of cut leaf. microscope (JOEL 6310). The 1st to 6th instars According to Basri and Kevan (1995), larvae use larvae, eggs and pupae were fixed in FAA for 66.8% of the leaf tissue removed from the oil palm 24 hours, washed in 1% cacodylate buffer and for growth and development and 33.2% for case post-fixed in 1% cacodylate-buffered osmium construction. The case was cone-shaped at the 1st tetroxide solution for two hours. The samples instar stage of the neonate (early stage instars), with were dehydrated in graded series of alcohol (30, closed distal end and open base for the neonate to 50, 70, 90, 95 and 100%), and Critical Point feed and discharge waste. The study showed that Drier Balzers using carbon dioxide liquid as an 60 – 90% of the neonates survived and developed intermediate fluid. Critical-point dried samples successfully into 2nd instar larvae. Hence, a mean were mounted on cylinder stubs and sputter- between 60 – 190 larvae successful developed to coated with gold, and then observed with a 2nd instar larvae per egg mass. scanning electron microscope JEOL 6310 at an The instars of the larvae can be identified acceleration voltage of 10 or 15kV. by the morphological architecture and length of the case, which corresponds to the length of the caterpillar. The larvae carried the case as it moved around to feed. The case surface of instar 1 was relatively smooth with an average length of 1.6 mm. J. Sustain. Sci. Manage. Volume 6 (1) 2011: 51-59 MICROSTRUCTURE AND LIFE CYCLE OF METISA PLANA WALKER 53 In instar 2, two-to-three tiny, rounded leaf pieces thorax (Plate 2). The entire body was covered were loosely attached at the basal end of the case. with sensory setae (Plate 3). Stemmata was well- The average length of the case was 4.6 mm, which differentiated, convex, approximately 50 µm had enlarged more than 100% from the 1st instar diameter and located laterally on either side of the case. The average length of the case at instar 3 was head capsule (Plate 4). The mouthpart of the larva 5.9 mm. The surface of distal half of the case had a consisted of the labrum, mandibles and maxillae. smooth surface, but the surface of the case toward The mandibles bit off plant material and tore it into the posterior end was disarranged, with four to six small, easily-digestible pieces. Inside the mouth rectangular leaf pieces attached at the proximal half was a pair of accessory jaws maxillas, sensory of the case. At instar 4, many loosely-attached large organ and a maxillary palp was attached to them round-to-rectangular leaf pieces were on the case for tasting the food (Plate 5). The labium was a pair surface. The average length of the case was 9.5 of plates, fused together to form the lower lip of the mm. At instar 5, most of the loose leaf pieces were mouth. The labrum functioned as the upper lip of plastered onto the case forming a relatively smooth the insect mouth. surface case, except for a few semi-rounded leaf The thorax of M. plana larva was easily pieces attached at the proximal base. The average distinguished as compared to caterpillars such as case size was 11.3 mm. At instar 6, the case surface Sibine megasomoides, Spodoptera frugiperda, etc. was smooth and no loose leaf piece were attached, The thorax was immediately behind the head and and they were whitish-grey in colour. The case possessed three pairs of true legs on the underside expanded in length and circumference and became (Plate 6). The thoracic legs were jointed with hooks cylindrical with an average length of 13.0 mm. As for mobility of the larvae.